a bit of code

test.c

/*
左“{”，右”}"括号各N个，请打印出所有正确的组合，比如当N=3，{}{}{}，{{{}}}，等为正确的组合。如果写的代码是recursive，能否用iterative再写一个；反之亦然。
*/

// gcc -std=c99 test.c && ./a.out

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <assert.h>


void
recursive(char *str, int *left, int *right, int n)
{
    assert(NULL != str && NULL != left && n >= 0);

    if (*right == n)
    {
       *str = '\0';
       printf("%s\n", str - 2 * n);
       return;
    }

    if (0 == *left)
    {
        *str = '{';
        *left = 1;
        recursive(str + 1, left, right, n);
    }
    else
    {
        if (*left < n)
        {
            *str = '{';
            *left += 1;
            recursive(str + 1, left, right, n);
            *left -= 1;
        }

        if (*left > *right)
        {
            *str = '}';
            *right += 1;
            recursive(str + 1, left, right, n);
            *right -= 1;
        }
    }
}

int
main(void)
{
    char str[10] = {0};
    int left = 0;
    int right = 0;
    int n = 3;

    recursive(str, &left, &right, n);

    exit(EXIT_SUCCESS);
}